Using a panel of 31 diagnostic nuclear SNP markers in 56 toad populations from the southern Alps and the northern and central Apennines, we document that the range of the spined toad, Bufo spinosus, extends along the Mediterranean coast from France into the northwest of Italy. This species, and the common toad B. bufo, engage in a unimodal hybrid zone, with B. spinosus at the higher and B. bufo at the lower altitudes of the Ligurian Alps. The width of 24.0 km observed in the Italian section of the long hybrid zone is narrower than documented in France (ca. 50 km). Using six mitochondrial SNP markers, we resolve several haplotype groups, with approximate distributions as ‘bufo-e2’ across the French–Italian border region, ‘bufo-e3’ in the Italian Alps, ‘bufo-e6’ in the Apennines and ‘spinosus’ with a single occurrence in Italy. Leer más.